It is also something of a myth that the Confederate States Army had only old scrap weapons until they captured quality guns from the Yankees.

True, the CS did use what they had, and some less formal soldiers preferred shotguns to rifles, but there is no record of any front-line C.S. unit being armed with junk. While some soldiers reported for duty with family shotguns and hunting rifles, by the time of the first battles, rifles captured from Union depots and arsenals had been distributed to front-line troops, and Gorgas had ammunition production well underway. By late 1861, arms from England began to come through; one ship carried 10,000 Enfield rifles for the C.S. Army, plus 4000 for state governments and 1000 short rifles for the C.S. Navy. Meantime, the U.S. was also buying Enfields and other European arms; their need was not as great, but one purpose in buying those weapons was to deny them to the Confederacy.

That one shipment also included 1 million rounds of .577 ammunition and 2 million percussion caps for the Enfields and 1000 rounds each for the Navy's short rifles. And similar shipments continued for several years until the Union got its blockade organized. The .577 Enfield was officially adopted by the C.S. Army and was so common in the U.S. Army that they began to issue only .577 ammo, which would function in both the .58 Springfield and the .577 Enfield rifles.

Did the Confederates use captured U.S. arms? Of course, but they did not depend solely on them; their main source of supply was Europe. One problem was that, as the war continued and Union forces began to use more "patent" guns (especially carbines), the C.S. had no way of manufacturing ammunition for many of them. But there is no record of any C.S. defeat due to lack of small arms or small arms ammunition.

Edited to add: There were local shortages of ammunition, as in all wars, and the C.S. transportation system was poor. Still, the Southern fighting man almost always had the means to fight. The main shortage in the C.S. Army was not arms and ammo, but food and clothing, especially shoes. And the shortages of both became more acute as Union forces captured or burned areas like the Shenandoah valley that supplied cloth, leather, and, of course, food. Worse, Southern farmers who had supplies refused, toward the end of the war, to sell them for Confederate money. It is to the credit of the C.S. government that they did not simply confiscate civilian property, even in Yankee territory; it was always paid for, even though the money was valueless outside the C.S. (and had little value even there

This is what General Porter had to say:

Fighting for the Confederacy, General Edward Porter Alexander,

Chapter 3, page 60

It was on the morning after the battle of Bull Run that Gen Beauregard sent for me and told me that I was promoted to the position of Chief of Ordnance of his Army…. My duties as chief of ordnance were to keep the whole army always supplied with arms and ammunition.

We had great trouble from the great variety of arms with which our troops were equipped both in small arms and artillery. Every regiment and every battery would have some apparently of all possible calibers and would want every possible variety of ammunition. They objected always to swapping and the matter only got better materially in the fall of 1862 when we captured enough rifled muskets from the enemy and enough good guns to supply all our deficiencies. We first got a full supply after Chancellorsville.

At the beginning we had not over 10 percent, if so many, of rifled muskets. The balance were old smooth bore muskets and some even had flintlocks.

Chapter 5 page 121

I was occupied in re accumulating supplies of ammunition & in improving our armament of small arms and of artillery, by our captures in the recent battles, as well as by all the arms we could make or get in through blockage. The great point desired was to equip all our infantry with the rifle musket, caliber 58/100 instead of the old fashioned smooth bore musket, caliber 69/100, which nine out of ten of our men had to start with. …My recollection is that Gettysburg was our first battle in which we were at last entirely rid of smooth bore muskets. The captured Federal guns, and artillery ammunition too, were much superior to most of ours….

Up to Gettysburg the South ended up retaining possession of most of the battlefields. If you look at the number of muskets picked up by the North at Gettysburg, about 35,000 after that battle, if the winning side could pick up 10,000, 20,000, or 30,000 muskets after a battle that have surely helped the Army of Northern Virginia in rearming. But as General Porter says, they did get muskets through the blockage.

Now just how many that got through the blockage arrived to the front line would be a interesting number. I have read that the South would have folded in 12 to 18 months without English supplies. However, given that in all the wars I have read about, every REMF gets a nice warm winter coat before one front line soldier gets one, the closest source of supply might have been the Union Army!